Method for producing polyetherpolyols in the presence of a multi-metal cyanide complex catalyst

ABSTRACT

Polyetherpolyols are prepared by reacting diols or polyols with ethylene oxide, propylene oxide, butylene oxide or a mixture thereof in the presence of a multimetal cyanide complex catalyst by a process which is carried out in a vertical upright cylindrical reactor comprising a jet nozzle which is arranged in the upper reactor region and is directed downward and via which the starting materials and the reaction mixture are fed in, and comprising a take-off, preferably in the lower reactor region, via which the reaction mixture is fed back to the jet nozzle in an external circulation by means of a pump via an equilibration container, comprising a concentric guide tube which extends over the total length of the reactor, except for the reactor ends, and comprising a heat exchanger integrated in the annular space.

The present invention relates to a process for the preparation ofpolyetherpolyols.

Polyetherpolyols are provided in large amounts, in particular for thepreparation of polyurethane foams. In the known preparation processes,polyetherpolyols are prepared as a rule from alkylene oxides in thepresence of a short-chain initiator using different catalysts, such asbases, hydrophobized double-layer hydroxides, acidic or Lewis acidsystems, organometallic compounds or multimetal cyanide complexes.

Heterogeneous multimetal cyanide complex catalysts are highly selectiveand active catalysts which are suitable in particular for thepreparation of flexible foam polyetherpolyols, in which a high molecularweight has to be achieved and in which long oxalkylation times arerequired. By using multimetal cyanide complex catalysts, the productioncosts can be reduced and at the same time high-quality polyetherpolyol,which can be further processed to give low-odor and hence high-qualitypolyurethane foams, can be obtained. It is known from the literaturethat secondary reactions which may lead to the formation of odorsubstances and unsaturated components scarcely occur.

However, the high activity has the result that the heat of reactioncannot be removed in conventional reactors. If the polyetherpolyolpreparation catalyzed via a multimetal cyanide complex is carried out instandard stirred kettles, the metering rates of alkylene oxide arelimited by the heat removal capacity of the heat exchanger.

U.S. Pat. No. 5,811,595 proposes an ideally mixed reactor having one ortwo heat exchangers, the polyetherpolyol being fed into the circulationstream of the heat exchanger and the ethylene oxide into the reactor.Mixing of the ethylene oxide with the liquid phase is achieved by meansof a nozzle.

The high circulation rate required for maintaining the high heat removalcapacity and the danger of mechanical damage to the heterogeneouscatalyst by the pump are disadvantageous in this process. Moreover, thehighly reactive ethylene oxide is introduced into the reactor in which,owing to the cooling coils used, in particular at low degrees offilling, and owing to the small exchange area, the heat removal is verypoor. Overheating due to the high reaction rate can occur, resulting indamage to the product. This may be reinforced by the poor mixing in thereactor.

EP-A-0 850 954 describes a process in which the reaction takes place inthe gas space above the reaction liquid. The polyetherpolyol iscirculated via a heat exchanger by means of a pump and is fed in throughnozzles. This results in a large liquid surface. At the same time,ethylene oxide and polyetherpolyol are metered in via nozzles. The largesurface results in good mass transfer and hence high reaction rates.

Owing to the high reaction rate which can be achieved using thisprocess, local excess temperatures in the individual droplets are to beexpected, which in turn result in damage to the product. Here too, thehigh circulation rate required for heat removal is not unproblematic forthe heterogeneously dispersed multimetal cyanide complex catalyst, andthe danger of damage cannot be ruled out.

The artificially enlarged gas phase furthermore constitutes a potentialdanger, in particular in the case of the ethoxylation, since freealkylene oxide is present in the gas phase. Ethylene oxide tends towardgas phase decomposition, which may lead to bursting of the reactor. Onthe other hand, when the polyetherpolyol or ethylene oxide is passedinto the liquid, rapid reaction of the alkylene oxide is likely owing tothe active multimetal cyanide complex.

EP-A-0 419 419 proposes a jet loop reactor, i.e. a reactor havinginternal loop flow and external pumped circulation, for alkoxylation ofalcohols having a low functionality with ethylene oxide. However, thehigh reaction temperatures of 165° C. and the low functionalities resultin low viscosities of the reaction mixture.

It is an object of the present invention to provide a process employingsimple apparatus for the preparation of polyetherpolyols in the presenceof multimetal cyanide complex catalysts with improvement of thespace-time yield and avoidance of local overheating and hence a higherdegree of secondary reactions, thus ensuring a high product quality.

We have found that this object is achieved by a process for thepreparation of polyetherpolyols by reacting diols or polyols withethylene oxide, propylene oxide, butylene oxide or a mixture thereof inthe presence of a multimetal cyanide complex catalyst.

In the invention, the reaction is carried out in a reactor of uprightcylindrical design, comprising a jet nozzle which is arranged in theupper reactor region and is directed downward and via which the startingmaterials and the reaction mixture are fed in, and comprising atake-off, preferably in the lower reactor region, via which the reactionmixture is fed back to the jet nozzle in an external circulation bymeans of a pump via an equilibration container, comprising a concentricguide tube which extends over the total length of the reactor, exceptfor the reactor ends, and comprising a heat exchanger integrated in theannular space.

The vertical, upright cylindrical reactor described in EP-A-0 419 419was developed in particular for low-viscosity liquid reaction mixtures,i.e. for liquids which have a viscosity substantially below 10 mPa·sunder reaction conditions.

In comparison, the inventors of the present process have surprisinglyfound that the reactor type disclosed in EP-A-0 419 419 can also be usedfor more highly viscous reaction media, such as the polyetherpolyols ofthe present invention. As a rule, polyetherpolyols have highviscosities, approximately in the range from 80 to 1500 mPa·s at roomtemperature and still above 20 mPa·s, frequently above 100 mPa·s, underreaction conditions (from about 100 to 130° C.). It is known that theboundary layer between heat exchanger and reaction mixture increaseswith increasing viscosity, with the result that the heat can be removedmore and more poorly. According to the novel process, in spite of thehigh viscosity, it was surprisingly possible to achieve sufficient heatremoval, so that high alkylene oxide metering rates could be realized,resulting in an improved space-time yield and hence higher productivityand good product quality. Local excess temperatures which might lead todamage to the product were avoided.

Moreover, in the reaction procedure with external pump circulation,deposition of catalyst in the external pump circulation and damage tothe catalyst by the pump would have been expected, with the result thatthe reaction would be slowed down since, owing to the low catalystconcentrations of less than 500 ppm used, even small losses of catalystcould lead to a considerable loss of activity. Furthermore, owing to theexternal pump circulation, a shift in the molecular weight distributionwould have been expected since part of the product always remains in theexternal circulation. Contrary to expectation, the disadvantagesmentioned were not observed and, on the contrary, a product having lowdispersity of the molar mass distribution, i.e. having excellent productquality, was obtained.

In reactors equipped with heat exchanger plates, there is the dangerthat heterogeneous catalyst will settle in corners, angles and otherareas with insufficient flow and consequently would no longer beavailable for the catalytic reaction or would be available only to aninsufficient extent. This problem is not quite so critical at relativelyhigh catalyst concentrations because a catalyst loss in this case doesnot have an extreme effect on the quality of the catalysis and of theproducts. On the other hand, at low catalyst concentrations, for example100 ppm or less, the loss of available catalyst of the order ofmagnitude of only a few 10 ppm constitutes a dramatic absolute loss ofcatalyst material and hence of catalyst activity. The consequence issubstantially poorer product quality, broader molecular weightdistribution and high molecular weight fractions. In contrast, it wassurprisingly found that, in the novel process, in spite of very lowcatalyst concentrations, such problems did not occur and there was nodeterioration in the product quality.

According to the invention, diols or polyols are fed together withethylene oxide, propylene oxide, butylene oxide or a mixture thereof, inthe presence of a multimetal cyanide complex catalyst, to a vertical,upright cylindrical reactor comprising heat exchanger plates throughwhich a heat-exchange medium flows, via a jet nozzle which is arrangedin the upper reactor region and is directed downward, and is fed back tothe jet nozzle via a take-off preferably arranged in the lower reactorregion, via an external circulation by means of a pump via anequilibration container.

The present invention has no restrictions with regard to the multimetalcyanide complex catalyst which can be used; it may be amorphous but ispreferably at least partly, predominantly or completely crystalline. Ifnecessary, the catalyst is supported.

Particularly preferred multimetal cyanide complex catalysts are those ofthe formula (I)

 M¹ _(a)[M²(CN)_(b)L¹ _(c)]_(d).e(M¹ _(f)X_(g)).hL².iH₂O  (I)

where

M¹ is at least one element from the group consisting of Zn(II), Fe(II),Co(III), Ni(II), Mn(II), Co(II), Sn(II), Pb(II), Fe(III), Mo(IV),Mo(VI), Al(III), V(IV), V(V), Sr(II), W(IV), W(VI), Cu(II), Cd(II),Hg(II), Pd(I), Pt(II), V(III), Mg(II), Ca(II), Sr(II), Ba(II) andCr(III),

M² is at least one element from the group consisting of Fe(II), Fe(III),Co(III), Cr(III), Mn(II), Mn(III), Ir(III), Rh(III), Ru(II), V(IV),V(V), Co(II) and Cr(II),

L¹ is at least one ligand from the group consisting of cyanide,carbonyl, cyanate, isocyanate, nitrile, thiocyanate and nitrosyl,

X is a formate anion, acetate anion or propionate anion,

L² is at least one water-miscible ligand from the group consisting ofalcohols, aldehydes, ketones, ethers, polyethers, esters, ureaderivatives, amides, nitrites and sulfides,

a, b, d, e, f and g are integers or fractions greater than zero and c, hand i are integers or fractions greater than or equal to zero, a, b, cand d being chosen so that the electroneutrality condition is fulfilledand f and g have been chosen so that the electroneutrality condition isfulfilled, whose X-ray diffraction pattern has reflections at at leastthe d values

6.10 Å±0.04 Å

5.17 Å±0.04 Å

4.27 Å±0.02 Å

3.78 Å±0.02 Å

3.56 Å±0.02 Å

3.004 Å±0.007 Å

2.590 Å±0.006 Å

2.354 Å±0.004 Å

2.263 Å±0.004 Å

if X is a formate anion, whose X-ray diffraction pattern has reflectionsat at least the d values

5.20 Å±0.02 Å

4.80 Å35 0.02 Å

3.75 Å±0.02 Å

3.60 Å±0.02 Å

3.46 Å±0.01 Å

2.824 Å±0.008 Å

2.769 Å±0.008 Å

2.608 Å±0.007 Å

2.398 Å±0.006 Å

if X is an acetate anion, and whose X-ray diffraction pattern hasreflections at at least the d values

5.59 Å±0.05 Å

5.40 Å±0.04 Å

4.08 Å±0.02 Å

3.94 Å±0.02 Å

3.76 Å±0.02 Å

3.355 Å±0.008 Å

3.009 Å±0.007 Å

2.704 Å±0.006 Å

2.381 Å±0.004 Å

if X is a propionate anion, or which have a monoclinic crystal system ifX is an acetate anion.

Such multimetal cyanide complex catalysts are described in DE-A-197 42978.

A multimetal cyanide complex catalyst of the zinc-cobalt type isparticularly preferably used.

The multimetal cyanide complex catalyst is preferably used in amounts ofless than 250 ppm, particularly preferably less than 100 ppm, inparticular less than 50 ppm, based on the mass of product to beproduced.

According to the invention, the process is carried out in a vertical,upright cylindrical reactor comprising a jet nozzle which is arranged inthe upper reactor region and is directed downward and via which thestarting materials and the reaction mixture are fed in, and comprising atake-off, preferably in the lower reaction region, via which thereaction mixture is fed back to the jet nozzle in an externalcirculation by means of a pump via an equilibration container,comprising a concentric guide tube which extends over the total lengthof the reactor, except for the reactor ends, and comprising a heatexchanger integrated in the annular space.

Such a reactor is described, for example, in German Patent Application19854637.8.

In such a reactor, an internal loop flow forms from top to bottom viathe downward-directed jet nozzle in the guide tube and from bottom totop in the annular space between guide tube and reactor interior. Thepredominant part of the reaction mixture is conveyed in this internalloop flow and only a small fraction of the reaction mixture is pumpedvia the external circulation and ensures, via the jet nozzle, that theloop flow is driven.

The ratio of volume flow rates of internal loop flow to external pumpedreaction mixture is from 2 to 30, preferably from 5 to 10.

The internal loop flow ensures ideal mixing with high temperatureconstancy and the absence of zones with alkylene concentration, wherelocal excess temperatures might occur owing to the higher velocities.Moreover, by means of the heat exchanger integrated in the annularspace, the heat of reaction is removed at its place of origin, resultingin a highly isothermal nature of the reaction, i.e. a very smalltemperature gradient over the reactor height. According to the novelprocess, restrictions of the reaction rate by mass transfer or heattransport can thus be virtually completely eliminated. Secondaryreactions which are otherwise promoted by temperature gradients in thereaction system are virtually completely suppressed.

In the preferred process variant, in which the predominant part of thereaction mixture is conveyed in the internal loop flow and only a smallfraction of the reaction mixture is pumped externally, substantiallysmaller amounts of catalyst are circulated per unit time via thecirculation pump. This leads to a reduction in the mechanical stress onthe catalyst and hence to a longer life.

In a preferred embodiment, the concentric guide tube has across-sectional area of from {fraction (1/10)} to half thecross-sectional area of the reactor. The jet nozzle is preferablyarranged above the upper end of the guide tube, in particular from ⅛ ofthe guide tube diameter to one guide tube diameter away, or dips intothe guide tube to a depth of up to several guide tube diameters.

As a rule, the guide tube is designed as a simple tube, but it is alsopossible to design the guide tube as a tubular plate-type heat exchangeror as a coiled cooling tube.

Preferably, an impact plate can be arranged in the reactor region belowthe lower end of the guide tube, preferably one guide tube diameteraway. The impact plate, together with the concentric guide tube,stabilizes the internal loop flow in the reactor. In addition to flowreversal, the impact plate ensures that no gas bubbles are entrainedinto the external circulation and damage the pump.

The heat exchangers integrated in the annular space are preferablydesigned in such a way that as far as possible they do not hinder theinternal loop flow and do not give rise to any turbulence. The heatexchangers used may be, for example, tubes through which a coolingmedium flows and which are preferably arranged parallel to the reactorwall, plate-type heat exchangers which are likewise preferably parallelto the reactor wall, or boiling tubes closed at the bottom, i.e. fieldtubes as described, for example, in EP-A-2 630 135. When field tubes areused, it is possible to use the resulting vapor as process vapor.

The jet nozzle is preferably in the form of a single-material nozzle. Inthis process variant, only the liquid reaction mixture is sprayed in andgas, for example nitrogen, and alkylene oxides from the gas space abovethe liquid level are dispersed in the liquid reaction mixture. Inaddition, an apparatus for feeding in one or more gaseous reactants,preferably one or more, in particular from 1 to 3, annular tubes havinga multiplicity of orifices, in particular distributed in the lowerreactor region or over the reactor height, can be provided in theannular space between guide tube and reactor interior. The advantage ofa single-material nozzle is its simple design.

In order to be able to take up the volume expansion of the reactionmixture as the reaction progresses, it is necessary to provide anequilibration container in the external circulation. The equilibrationcontainer used may be a static mixer or a stirred kettle, in which thereaction mixture is ideally mixed. At the beginning of the reaction, theequilibration container is empty and the initiator is initially takentogether with the multimetal cyanide complex catalyst in the reactor. Inorder to reduce the cycle times, the initiation of the catalyst, i.e.the activation of the catalyst with the alkylene oxides, can be effectedin a separate container. After the initiation, the active multimetalcyanide complex catalyst/initiator mixture can be further dilutedwithout substantially reducing the activity of the catalyst. In order tobe able to take up the volume expansion to 3 to 100, preferably 5 to 50,times the volume, which is to be expected in the case of flexible foampolyols, the container must be larger than the volume of the reactor bythe appropriate factor. Owing to the high activity of the multimetalcyanide complex catalyst, there is unlikely to be any accumulation ofalkylene oxide in the equilibration container since the alkylene oxideundergoes complete reaction in the reactor itself. The pressure in theequilibration container is kept constant by means of nitrogen. Removalof heat is not required since the heat is removed in the reactor itself.After the end of the alkoxidation, reactor and equilibration containerare emptied and the product is further worked up.

The reaction in the reactor preferably takes place at from 90 to 200° C.and from 1 to 50 bar.

Particularly preferably, the reaction is carried out at from 110 to 140°C. and from 2 to 10 bar.

The power input is preferably from about 15 to 30 kW/1 at the nozzle andfrom 3 to 10 kW/1 in the total reaction system.

By dispersing the individual reactants and in combination with the otherreaction parameters, thorough mixing of all components at low substrateconcentrations and with high mass transfer coefficients and largevolume-specific phase interfaces is achieved. The arrangement of heatexchangers in the annular space, preferably parallel to the reactorwalls, results in virtually complete freedom from gradients in thereactor contents with respect to the reaction temperature. By avoidinglocal overheating, secondary reactions are substantially suppressed andcatalyst deactivation is substantially avoided. Consequently, highspace-time yields are achieved in combination with an improvement in theproduct quality.

The invention is explained in more detail below with reference to anembodiment.

EXAMPLE

A cylindrical reactor having a total volume of 12 m³ was used, the guidetube having a length of 5.80 m and a diameter of 0.2 m. 460 field tubeshaving a length of 6.50 m and an external diameter of 3 cm were used asa heat exchanger in the annular space. 2.49 kg/s of propylene oxide and0.2 kg/s of polyetherol having a molar mass of 400 g/mol were fedcontinuously to the reactor.

The preparation of the multimetal cyanide catalyst was carried out in atwo-stage process in which first the acid and then the catalyst wereobtained through precipitation. For this purpose, 7l of strongly acidicion exchanger which was in the sodium form, i.e. Amberlite® 252 Na fromRohm & Haas, were introduced into an exchanger column having a length of1 m and a volume of 7.7l. The ion exchanger was then converted into theacid form by passing 10% strength hydrochloric acid at a rate of 2 bedvolumes per hour over the exchanger column for 9 hours until the sodiumcontent in the discharge was <1 ppm. The ion exchanger was then washedwith water. The regenerated ion exchanger was then used to prepare anessentially alkali-free hexacyanocobaltic acid. For this purpose, a 0.24molar solution of potassium hexacyanocobaltate in water was passed overthe ion exchanger at a rate of one bed volume per hour. After 2.5 bedvolumes, a changeover was effected from the potassium hexacyanocobaltatesolution to water. The 2.5 bed volumes obtained had on average a contentof 4.5% by weight of hexacyanocobaltic acid and alkali contents of <1ppm.

For the preparation of the catalyst, 8553.5 g of zinc acetate solution(content of zinc acetate dihydrate: 8.2% by weight, content of Pluronic®PE 6200, i.e. a block copolymer of ethylene oxide and propylene oxide,which was used for controlling the crystal morphology: 1.3% by weight)were then initially taken in a 20l reactor and heated to 60° C. whilestirring. 9956 g of hexacyanocobaltic acid solution (cobalt content 9g/l, content of Pluronic® PE 6200: 1.3% by weight) were then added inthe course of 20 minutes at 60° C. with continuous stirring. Thesuspension obtained was stirred for a further 60 minutes at 60° C.Thereafter, the solid thus obtained was filtered off and was washed with6 times the cake volume. The moist filter cake was then dispersed inpolypropylene glycol having a molar mass of 400 g/mol.

The dispersion thus obtained was used as a catalyst. The catalystconcentration was 60 ppm and the reactor temperature could be keptconstant at 125 ±0.2° C. over the complete reactor length. The averagemolar mass achieved was 5200 g/mol, and high molecular weight componentswere not detected. Amaximum space-time yield of 807 kg/m³/h wasachieved.

In an analogous comparative experiment in a 200l stirred kettle reactorwith external heat exchanger, a maximum space-time yield of 450 kg/m³/hwas achieved at the same catalyst concentration, owing to the limitedheat removal capacity. In both cases, a cycloacetal content of 0.04 ppmand a content of unsaturated components of 0.005 meq/g were achieved.Completely symmetrical molecular weight distribution was obtained.

In a comparative experiment under KOH catalysis (0.3% by mass), aspace-time yield of 105 kg/m³/h was achieved in an analogous synthesis,the cycloacetal concentration was 4.8 ppm and the concentration ofunsaturated components was 0.061 meq/g. Furthermore, high molecularweight components were detected.

The novel process thus permitted a significantly higher space-time yieldwith the same product quality.

The experiment was repeated using the reactor with equilibrationcontainer, the same product properties being obtained. The space-timeyield was 790 kg/m³/h, without taking into account the times of loadingand unloading the reactor.

We claim:
 1. A process for the preparation of polyether polyols byreacting diols or polyols with ethylene oxide, propylene oxide, butyleneoxide or a mixture thereof in the presence of a multimetal cyanidecomplex catalyst, wherein the reaction is carried out in a reactor ofupright cylindrical design, comprising a jet nozzle which is arranged inthe upper reactor region and is directed downward and via which thestarting materials and the reaction mixture are fed in, and comprising atake-off, via which the reaction mixture is fed back to the jet nozzlein an external circulation via means of a pump via an equilibrationcontainer, comprising a concentric guide tube which extends over thetotal length of the reactor, except for the reactor ends, and comprisinga heat exchanger integrated in the annular space.
 2. A process asclaimed in claim 1, wherein the concentric guide tube has across-sectional area of from {fraction (1/10)} to half thecross-sectional area of the reactor and wherein the jet nozzle isarranged above the upper end of the guide tube, or dips into the guidetube to a depth of up to several guide tube diameters.
 3. A process asclaimed in claim 1 or 2, wherein the predominant part of the reactionmixture, corresponding to 2 to 30 times the volume flow of theexternally circulated reaction mixture, flows in an internal loop flowthrough the guide tube from top to bottom and through the annular spacebetween guide tube and reactor inner wall from bottom to top.
 4. Aprocess as claimed in claim 1, wherein the reaction is carried out atfrom 90 to 200° C. and from 1 to 50 bar.
 5. A process as claimed inclaim 1, wherein the reaction is carried out at from 110 to 140° C. andfrom 2 to 10 bar.
 6. A process as claimed in claim 1, wherein themultimetal cyanide complex catalyst is used in a concentration of lessthan 250 ppm, preferably less than 100 ppm, more preferably less than 50ppm, based on the mass of product to be produced.
 7. A process asclaimed in claim 1, wherein the jet nozzle is in the form of asingle-material nozzle and wherein additionally, if required, anapparatus for feeding in one or more gaseous reactants, preferably oneor more, in particular from 1 to 3, annular tubes having a multiplicityof orifices, in particular distributed in the lower reactor region orover the reactor height, is (are) provided in the annular space betweenguide tube and reactor inner wall.
 8. A process as claimed in claim 1,wherein an impact plate is arranged in the reactor region below thelower end of the guide tube, preferably one guide tube diameter away. 9.A process as claimed in claim 1, wherein the multimetal cyanide complexcatalyst is of the formula (I) M¹ _(a)[M²(CN)_(b)L¹ _(c)]_(d).e(M¹_(f)X_(g)).hL².iH₂O  (I) where M¹ is at least one element from the groupconsisting of Zn(II), Fe(II), Co(III), Ni(II), Mn(II), Co(II), Sn(II),Pb(II), Fe(III), Mo(IV), Mo(VI), Al(III), V(IV), V(V), Sr(II), W(IV),W(VI), Cu(II), Cd(II), Hg(II), Pd(II), Pt(II), V(III), Mg(II), Ca(II)Sr(II), Ba(II) and Cr(III), M² is at least one element from the groupconsisting of Fe(II), Fe(III), Co(III), Cr(III), Mn(II), Mn(III),Ir(III), Rh(III), Ru(II), V(IV), V(V), Co(II) and Cr(II), L¹ is at lastone ligand from the group consisting of cyanide, carbonyl, cyanate,isocyanate, nitrile, thiocyanate and nitrosyl, X is a formate anion,acetate anion or propionate anion, L² is at least one water-miscibleligand from the group consisting of alcohols, aldehydes, ketones,ethers, polyethers, esters, urea derivatives, amides, nitriles andsulfides, a, b, d, e, f and g are integers or fractions greater thanzero, c, h and i are integers or fractions greater than or equal tozero, a, b, c and d being chosen so that the electroneutrality conditionis fulfilled and f and g have been chosen so that the electroneutralitycondition is fulfilled, whose X-ray diffraction pattern has reflectionsat at least the d values 6.10 Å±0.04 Å 5.17 Å±0.04 Å 4.27 Å±0.02 Å 3.78Å±0.02 Å 3.56 Å±0.02 Å 3.004 Å±0.007 Å 2.590 Å±0.006 Å 2.354 Å±0.004 Å2.263 Å±0.004 Å if X is a formate anion, whose X-ray diffraction patternhas reflections at at least the d values 5.20 Å±0.02 Å 4.80 Å±0.02 Å3.75 Å±0.02 Å 3.60 Å±0.02 Å 3.46 Å±0.01 Å 2.824 Å±0.008 Å 2.769 Å±0.008Å 2.608 Å±0.007 Å 2.398 Å±0.006 Å if X is an acetate anion, and whoseX-ray diffraction pattern has reflections at at least the d values 5.59Å±0.05 Å 5.40 Å±0.04 Å 4.08 Å±0.02 Å 3.94 Å±0.02 Å 3.76 Å±0.02 Å 3.355Å±0.008 Å 3.009 Å±0.007 Å 2.704 Å±0.006 Å 2.381 Å±0.004 Å if X is apropionate anion, or which have a monoclinic crystal system if X is anacetate anion.
 10. A process as claimed in claim 1, wherein themultimetal cyanide complex catalyst is substantially or completelycrystalline.
 11. A process as claimed in claim 1, wherein a multimetalcyanide complex catalyst of the zinc-cobalt type is used.
 12. A processas claimed in claim 1, wherein the take-off is arranged in the lowerreactor region.
 13. A process as claimed in claim 2, wherein the jetnozzle is arranged above the upper end of the guide tube from ⅛ of theguide tube diameter to one guide tube diameter away.
 14. A process asclaimed in claim 3, wherein the predominant part of the reaction mixturecorresponds to 5 to 10 times the volume flow of the externallycirculated reaction mixture.